Diaza crown ethers are well known materials useful as chelating agents for selective binding and extraction of cations and as antioxidants. A number of other uses are recited in the recent review article by K. E. Krakowiak, et al., "Synthesis of Aza-Crown Ethers," Chemical Reviews, Vol. 89, No. 4, 1989, pp. 929-972, 944, including use as key intermediates in the synthesis of cryptands and other N-substituted ligands.
Unfortunately, previous routes to producing the diaza crown ethers, for example the diaza-18-crown-6, are very tedious and expensive, as outlined in the K. E. Krakowiak, et al. article. This publication notes that diaza crown ethers can be prepared by several different routes, for example, reacting 1,2-bis(2-haloethoxy)ethane or triethylene glycol ditosylates with triethylene glycol diamine or bis(tosylamides) followed by removal of the pendant tosyl groups, if required. Another route concerns reacting a primary amine with a 1,2-bis(2-haloethoxy)ethane followed by removal of the pendant alkyl groups; or reacting triethylene glycol diamine with triglycolyl dichloride. A number of other methods are described.
V. J. Gatto, et al. in "4,13-Diaza-18-Crown-6 (1,4,10,13-Tetraoxa-7,16-diazacyclooctadecane)," Organic Synthesis, Vol. 68, 1989, pp. 227-233, teach the preparation of the title compound by a three-step procedure that might be considered the standard preparation for these materials. First, benzylamine is reacted with 1,2-bis(2-chloroethoxy)ethane to produce 1,10-dibenzyl-4,7-dioxa-1,10-diazadecane. The product of the first step is then reacted in the presence of 1,2-bis(2-iodoethoxy)ethane, anhydrous sodium carbonate and sodium iodide in acetonitrile to give N,N'-dibenzyl-4,13-diaza-18-crown-6 in the second step. The phenyl groups of the second step product are then removed in a third, hydrogenation step over a palladium catalyst on a carbon support.
The first reference for the preparation of hexaethylene glycol triamine (3,6,12,15-tetraoxa-9-azaheptadecane-1,17-diamine), which is used in the invention herein, is by A. P. King, et al., "Secondary Amines from Trifluoroacetamides, " Journal of Organic Chemistry, Vol. 39, No. 9, 1974, pp. 1315-1316. It was prepared, along with other compounds including a small amount of 4,13-diaza-18-crown-6, by reaction of 1,8-dichloro-3,6-dioxaoctane and ammonia.
Somewhat related are U.S. Pat. Nos. 4,864,062 and 4,906,783 which produce linear, rather than cyclic amines. For example, a process for producing dioctamethylene triamine is disclosed in U.S. Pat. No. 4,864,062 which comprises dimerizing octamethylene diamine in the presence of a zeolite catalyst represented by the formula: Na.sub.2 O.xSiO.sub.2.yAl.sub.2 O.sub.3 where x and y are so selected that the molar ratio of Na.sub.2 O to Al.sub.2 O.sub.3 is in the range of 0.02 to 0.05 and the molar ratio of SiO.sub.2 to Al.sub.2 O.sub.3 is in the range of 1 to 10. U.S. Pat. No. 4,906,783 describes the preparation of bis(hexamethylene)triamine from 6-aminohexanenitrile by catalytically preparing di(5-cyanopentyl)amine, followed by hydrogenation using a nitrile hydrogenation catalyst. The first reaction uses at least one metal selected from the class consisting of palladium, platinum, rhodium and ruthenium. The second reaction uses a nitrile hydrogenation catalyst such as Raney cobalt, Raney nickel, supported cobalt, supported nickel and iron oxide.
As may be seen by reviewing the above-noted preparations, diaza crown ethers prepared by conventional methods often require more than one step, high dilution conditions and more than one reagent. All of these considerations increase the cost of the produced crown ethers. It would be desirable if diaza crown ethers could be prepared by a one-step procedure which did not require high dilution.